Diaphragm for fuel pumps and method of making same



Patented Mar. 1, 1932 I UNITEDSTATES PATENT OFFICE DONALD W. RANDOLPH AND JAY T. FORD, OF FLINT, MICHIGAN, ASSIGNORS TO A C SPARK PLUG COMPANY, OF FLINT, MICHIGAN, A COMPANY OF MICHIGAN DIAPHRAGM FOR FUEL PUMPS AND METHOD OF MAKING SAME No Drawing.

ing fabric materials order to obtain the n desirable physical and chemical properties.

The cloth fabric must be strong enough to withstand repeated flexings and must be coated in such a manner as to be impervious to air as well as gasoline, or other liquid ltfuels. The coating must also be practically insoluble in liquid fuels. The coating as well as the fabri'c ba se must resist the action'of repeated flexing and also must have a minimum change in flexibility with changes in operating temperatures. In particular the coated fabric must not become greatly stifi'- ened and thus lose flexibility upon prolonged exposure to temperatures 20 below zero Fahrenheit or lower. p

All of the above qualities are especially es sential in diaphragms for fuel pumps used on automobile engines if the pump is to give the owner of the car uninterrupted carefree service over periods. of years and in all kinds of climates. y

In order to obtain these desirable physical and chemical properties it is essential, first, that a suitable textile material be employed in the diaphragms. While there is, of course, more or less latitude in the weave of the fabrio. and the material of which it is composed, we have found that the most suitable textile material uponwhich to apply the coating is a mercerized cotton fabric closely woven from two-ply yarn so. as tohave at least 80 threads per inch in each direction, thus forming what is known as a square woven cloth.

Such fabric, properly woven, has-a tensile strength of at least 80 pounds per inch width.

cient amount of the coating, it is essential that it be relatively free from starch. We have found it desirable to keep the starch content of the uncoated cloth-under 1%.

The cloth must likewise be .free from traces In order that the cloth may absorb a sufli- Application filed December 18, 1929. Serial No. 415,116.

of acid, which tends to weaken the fabric by slow attack, and the moisture content of the cloth must not be more than about 1%.

The fabric is obtained in large rolls and the next step consists in the coating of the cloth to render it impervious to gasoline,

benzol, and the like, Without rendering it too stifl' for efficient use. In coating the cloth it is preferably fed through rollers into a tank containing the material for the first or base coat, is then passed through a drying oven; two coats are then applied to each side of the cloth. Drying is carried out between each successive coatings. Our invention has as one of its special objects the control of the drying operations to insure a uniform product, which will be neither too stifi nottoo soft, and the details of this systemof control will now be described.

A The first,or base coat consists of drying oils preferably applied with a suitable non-drying and non-volatile thinner. We have used with success mixtures of boiled tung oil with boiled linseed oil or boiled rubber seed oil. Such raw or partially oxidized oils which dry to a characteristic tough film are themselves soluble in gasoline and other solvents in the raw state. The film produced by dry- .ing of the oils, however, isnot soluble in ordinary solvents and the extent of solubility decreases with the extent of the drying op and perhaps other chemical changes are involved. V

The raw oils,after being mixed together, are preferably partial y dried by heating to a temperature of 200 At the same time a stream of air is passed through the oil, until the iodine number of the oil is reduced to 150 to 160 (Wij's method). Thismethod is de-- scribed in a Technical Methods of Analysis,

. R. C. Griffin, 1st edition,p. 241.

The mixture of oilswe have found most advantageous for, coating is composed' of equal parts by'volume of linseed oil and tung to d example of such a thinner is oleum spirits,

a product of the Standard Oil Company which has an initial boiling point of 147 F a 10% point of 309 F., and a 90% point of 392 F.

The purpose of a thinner of either class A or class B .is to increase the flexibility of the coating at low temperatures, the dryingoperation preferably not being carried to apoint where the thinner of class A is appreciably dried or any considerable part of the thinner of class B is removed by evaporation.

' The first coat is applied as previously stated, by running the strip material through a bath containing the oils until asquare yard of the cloth, absorbs approximately 2.7 ounces of the oils. The cloth is then passed through a drying oven for a sutlicient length of time, and with the oven maintained at a sufficient temperature so that it is dried only to the point where it ceases to be sticky.

It is very important that the drying be carried justfar enough to produce a rela-- tively insoluble oil film and not so far as to make the cloth so stifi at low temperatures as to interfere withthe operation of the pump. We have succeeded in achieving accurate control by specifying the amount of iodine that will be absorbed by, one hundred grams of the oil coating, since the iodine adsorption is a measure of the state of dryness of the coating. The iodine number for the cloth thus coated is kept between 5 and 15 grams per 100 grams of coating, by controlling the drying time and temperature in an suitable manner. In actual practice we ave employed, with the specific cloth and composition described which is applied in three coats, rying oven temperatures around 150 F and have continued the dryin treatment for 8 to 10 hours. Qbviously if t e temperature is increased, the time may be shortened and vice versa. But for best results the temperature should in no case exceed 160 F., particularly in drying the first coat where a nond ing thinner is used.

t will be found that a coating applied as described will thorou hly impregnate the fibers of the cloth and that the oil completely closes the pores of the fabric, making it airtight.

The second and third coats are each up lied to both sides of the fabric simultaneous y as by running the fabric over a roller or rollers which are immersed in the oils. It has been .found by experience that the second and third coats should be made without thinner as the solubility of the surface coating is less when the thinner is left out, and the flexibility of the finished cloth is not decreased.

By the second coating the oil content of the material is increased until a square yard of the original cloth has absorbed additional oil to the amount of 1.5 ounces. The dryin after the second coat is accomplished in the same manner as after the first and is carried to the point where 15 to 20 grams of iodine are absorbed per hundred grams of coating. In the specific example given, the second drying may be carried on at approximately 150 F. for a period of 8 to 10'hours.

The third coat is of the same composition and is applied in the same manner as the second, and is such as to bringthe weight of the coated cloth to at least 8.8 ounces per square yard. In other words, a s uare yard of the original cloth has now absor' d a total of 5 ounces of oil. The drying of the third coat is carried to the point where the iodine number of the finished coating is 6 to 15 grams of iodine per grams of coating;

The drying may be accomplished by exposing the cloth to even temperatures around 150 F. for a period of 8 to 10 hours.

We have foundby exhaustive tests that with an iodine numberbelow 6, diaphragms for commercial fuel pumps are so still as to require so many strokes to feed a given volume of fuel that the engines supply is seriously interfered with, The result is poor engine operation. We have likewise found by tests that with an iodine value above 15. the solubility of thecoating in gasoline becomes excessive and it becomes sosoftas to rub off in handling, particularly when exposed to gasoline, kerosene or the like.

Diaphragms are now out from the finished fabric, each diaphragm comprising a number of layers of the coated cloth. Before assembling the diaphragms in the pump we have found it necessary to further soften the cloth coating by immersion in kerosene for a period of about twent minutes. The action of the kerosene is suc as to soften the coating and reduce its tendency to sti'lfen at low operating tem eratures.

Wi e want to particularly emphasize the importance of accurate control of drying as set forth in this application. Without this the coated fabric will be found to vary in physical properties to such extremes that the coating will rub oil because of its softness or it will become so stifi at lower temperatures that it will not be flexible enough to "function properly. We have found it to be impossible to obtain a satisfactory commercial product have found the specific cloth treatment herein described to be best.

In the specification we havereferred to both linseed and rubber seed oils as being usable interchangeably in conjunction with tung oil to produce a satisfactory coating. In the absence of an established class name, we have used the phrase oil selected from a group consisting of linseed oil and rubber seed oil as descriptive of eitherof the oils alone or a combination of the two.

We claim:

1. A diaphragm for fuel pumps comprising cloth impregnated with a partially dried mixture of tung and rubber seed oils.

2. A diaphragm for fuel pumps comprising cloth impregnated with a partially dried mixture of tung oil and oil selected from a group consisting of linseed oil and rubber seed oil in substantially the proportions of 1 to 1 by volume.

3. A diaphragm for fuel pumps comprising cloth impregnatedwith a coating of a partially dried mixture of tung oil and oil selected from a group consisting of linseed oil and rubber seed oil in substantially the proportions of 1 to 1, applied with a thinner, to render it impervious to air and insoluble in liquid hydrocarbon fuels, said cloth having on its surfaces a dried layer of the said oils, applied without a thinner.

4. A diaphragm for fuel pumps comprising cloth impregnated with a coating of a partially dried mixture of tung oil and oil selected from a group consisting of linseed oil and rubber seed oil in substantially the proportions of 1 to 1, applied with a thinner, to render it impervious to air and insoluble in liquid hydrocarbon fuels, said cloth having on its surfaces dried layers of the said oils in the same proportions and applied without a thinner.

5. A diaphragm for fuel pumps comprising fabric rovided with a partially dried coating of rying oils, the coating having an iodine number of from 6 to.15. I

6. A diaphragm for fuel pumps made of fabric substantially free of starch, acid and moisture, and provided with a partially dried coating of drying oils having an iodine number of from 6 to 15.

7. A diaphragm for fuel pumps made of fabric substantially free of starch, acid and moisture, and provided with a partially dried coating of a mixture of tung oil and oil selected from a group consisting of linseed oil and rubber seed oil, the coating having an iodine number of from 6 to 15.

8. A diaphragm for fuel pumps made .Of

fabric substantially free ofstarch, acid' and moisture and impregnated and coated with a partially dried coating of a mixture of tung oil and oil selected from a group consisting of linseed oil and rubber seed oil. 7

9. The method of making a fuel pump diaof linseed oil and rubber seed oil, and drying the cloth until the coating shows an iodine number of from 6 to 15.

10. The method of making a fuel pump diaphragm adapted to resist the action of hydrocarbon fuels and to remain flexible throughout a wide temperature range consists in impregnating fabric with a mixture of tung oil, oil selected from a group consisting of linseed oil and rubber seed oil, and a non-volatile thinner, drying the treated cloth, and coating it with a mixture of the said oils applied without the thinner, and so drying the coated cloth that the coating shows an iodine number of from 6 to 15. I

11. The method of making a fuel pump diaphragm adapted to resist hydrocarbon fuels and to remain flexible throughout a wide temperature range which consists in thoroughly impregnating fabric with a mixture of tung oil and oil selected from a group consisting of linseed oil and rubber seed oil in substantially the proportions of 1 to 1 by volume, applied with a suitable thinner, partially drying the impregnated fabric, coating the impregnated fabric with a mixture of the oils in the same proportions and drying the coated and impregnated fabric until the coating has an iodine value of 6 to 15.

12. The method of making a fuel pump diaphragm adapted to resist the action of hydrocarbon fuels and to remain flexible throughout a wide temperature range which consists inimpregnating fabric with a mixture of tung oil, oil selected from a group consisting of linseed oil and rubber seed oil, and a thinner, drying the fabric until the coating shows an iodine number of 20 to 30, applying a mixture of the said oils to opposite sides of the fabric ing shows an iodine number of from 6 to 15'.

13. The method of making a fuel pump diaphragm adapted to resist the action of hydrocarbon fuels and to remain flexible throughout a wide temperature range which consists in impregnating fabric with a mixture of tung oil, oil selected from a group consisting of linseed oil and rubber seed oil, and a thinner, drying the fabric until the coating shows an iodine number of 20 to 30, applying a mixture of the said oils to both sides of the treated fabric, and drying the coating until it shows an iodine number of from 15 to 20, applying a third coating of the mixture of the said oils to both sides of the treated fabric and drying the fabric until the coating shows an iodine number of from 6 to 15.

14. The method of making a fuel pump diaphragm adapted to resist hydrocarbon fuels and to remain flexible throughout a wide temperature range which consists in thoroughly impregnating and coating fabric with a partially dried mixture of drying oils, and softening the coating by immersing the diaphragm in a suitable liquid for a short period prior to assembly, whereby the liquid together with the fuel in contact with the diaphragm assist in maintaining the flexibility of the diaphragm during use.

15. A coated fabric resistant to the action of hydrocarbonfuels and the like consisting of cloth impregnated with a, partially dried mixture of tung and rubber seed oils.

In testimony whereof we atfix our signatures.

JAY T. FORD. DONALD W. RANDOLPH. 

